Synthesis, Preclinical Validation, Dosimetry, and Toxicity of 68Ga-NOTA-Anti-HER2 Nanobodies for iPET Imaging of HER2 Receptor Expression in Cancer

Journal of Nuclear Medicine

Catarina Xavier¹  Ilse Vaneycken¹  Nick Devoogdt¹  Serge Muyldermans¹  Marleen Keyaerts¹  Tony Lahoutte¹  Johannes Heemskerk¹  Matthias D’huyvetter¹  Vicky Caveliers¹  Cécile Vincke¹ 

关键词: ⁶⁸Ga;    Nanobodies;    HER2;    iPET;    NOTA;   

DOI  :  10.2967/jnumed.112.111021

学科分类：医学（综合）

来源: Society of Nuclear Medicine

【 摘 要 】

Nanobodies are the smallest fully functional antigen-binding antibody fragments possessing ideal properties as probes for molecular imaging. In this study we labeled the anti–human epidermal growth factor receptor type 2 (HER2) Nanobody with 68Ga via a 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) derivative and assessed its use for HER2 iPET imaging. Methods: The 2Rs15dHis6 Nanobody and the lead optimized current-good-manufacturing-practice grade analog 2Rs15d were conjugated with S-2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) to enable fast and efficient 68Ga labeling. Biodistribution and PET/CT studies were performed on HER2-positive and -negative tumor xenografts. The effect of injected mass on biodistribution was evaluated. The biodistribution data were extrapolated to calculate radiation dose estimates for the adult female using OLINDA software. A single-dose extended-toxicity study for NOTA-2Rs15d was performed on healthy mice up to a dose of 10 mg/kg. Results: Radiolabeling was quantitative (>97%) after 5 min of incubation at room temperature; specific activity was 55–200 MBq/nmol. Biodistribution studies showed fast and specific uptake (percentage injected activity [%IA]) in HER2-positive tumors (3.13 ± 0.06 and 4.34 ± 0.90 %IA/g for 68Ga-NOTA-2Rs15dHis6 and 68Ga-NOTA-2Rs15d, respectively, at 1 h after injection) and high tumor-to-blood and tumor-to-muscle ratios at 1 h after injection, resulting in high-contrast PET/CT images with high specific tumor uptake. A remarkable finding of the biodistribution studies was that kidney uptake was reduced by 60% for the Nanobody lacking the C-terminal His6 tag. The injected mass showed an effect on the general biodistribution: a 100-fold increase in NOTA-2Rs15d mass decreased liver uptake from 7.43 ± 1.89 to 2.90 ± 0.26 %IA/g whereas tumor uptake increased from 2.49 ± 0.68 to 4.23 ± 0.99 %IA/g. The calculated effective dose, based on extrapolation of mouse data, was 0.0218 mSv/MBq, which would yield a radiation dose of 4 mSv to a patient after injection of 185 MBq of 68Ga-NOTA-2Rs15d. In the toxicity study, no adverse effects were observed after injection of a 10 mg/kg dose of NOTA-2Rs15d. Conclusion: A new anti-HER2 PET tracer, 68Ga-NOTA-2Rs15d, was synthesized via a rapid procedure under mild conditions. Preclinical validation showed high-specific-contrast imaging of HER2-positive tumors with no observed toxicity. 68Ga-NOTA-2Rs15d is ready for first-in-human clinical trials.

【 授权许可】

Unknown